Ser. RHoposPERME®. Fam. Ceramiee. 
Pirate CXCI. 
 PTILOTA SERICEA, Gunel. (sp) 
Gen. Cuan. Frond inarticulate, linear, compressed, or flat, distichous, 
pectinato-pinnate; the pinnules sometimes articulate. Fructifica- 
tion, of two kinds on distinct individuals; 1, ¢e¢raspores attached 
' to, or immersed in, the ultimate pimnules; 2, roundish, clustered 
receptacles ( favelle) surrounded by an involucre of short ramuli. 
Pritora (4g.),—from mers, pinnated. 
Pritora sericea ; frond flaccid, excessively branched ; secondary branches 
bi-tripmmate ; pinne and pinnules exactly opposite, the latter linear, 
composed of a single row of cells; tetraspores on short processes of 
the pimnules ; favellz: pedunculate, bate, naked, or surrounded with 
a few wregular ramuli. 
Pritota elegans, Kitz. Phyc. Gen. p. 378. 
Prizota plumosa, var. y. tenuissima, 4y. Sp. Alg. vol.i. p. 386. Ag. Syst. 
p- 195. 
Pritota plumosa, f. capillaris, Grev. Alg. Brit. p. 155. Hook. Fl. Br. vol. ii. 
p. 307. Wyatt, Alg. Danm. no. 77. Harv. in Mack. Fl. Hib. part 3. p. 204. 
Harv. Man. p. 84. 
Fucus sericeus, Gm. Hist. Fuc. p. 149. t. 15. f. 3. 
Fucus Ptilotus, Gunn. Fl. Norv. vol. ii. p. 135. t. 2. f. 15. Esper. Ie. 
p- 96. t. 46. 
Fucus pectinatus, Gunn. Fl. Norv. vol. ii. p. 122. t.2. f.8. Esper. Ic. 
p- 97. t. 47. 
_ Pxocamivcm elegans, Bory, sec. Kitz. 
_ Has. On the perpendicular faces of rocks, between tide marks; rarely on 
the stems of Fucus serratus. Perennial. Summer and autumn. Very 
common on the British shores. 
Geoer. Distr. Atlantic shores of Europe, from Norway to France. East coast 
of North America. 
Descr. Root, a small disk. Fronds tufted, two to four inches long, or more, 
and as much in expansion, distichous, excessively branched, in a more or 
less regularly pinnate manner, the main divisions only being somewhat 
dichotomous ; secondary branches elongate, repeatedly and closely pinnate, 
the pinne and pinnule nearly horizontally patent, of very irregular lengths, 
short and long being intermixed consecutively without order; the longer 
again and again pinnated, the shorter simple. Ultimate pinnule very closely 
set, those on the outer side of the pimne longer than the imner, linear, 
blunt, slightly curved, articulated, composed of a single row of quadrate 
cells; the older ones emitting pinnules of a second order at each joint, in 
which case the cells of the main pinnule acquire an invertly pyriform shape 
(owing to the excavation of two lateral buds). Zetraspores spherical, with 
wide borders, borne on the lateral processes of the pinnules. Favelle on 
VOL. II. Ss 
